RADIOISOTOPES IN THE TREATMENT OF BONE METASTASES

Systemic radionuclide therapy is gaining popularity in the radiotherap y community and changing the management of painful osseous metastases. This form of therapy has two major advantages: (i) it addresses all s ites of involvement; and (ii) selective absorption limits normal tissu e dose. As a result, toxicity is reduced and the therapeutic ratio inc reased. The biokinetics, dosimetry, and clinical experience with these compounds are reviewed. To date, the best studied and most commonly u sed radionuclide is strontium-89. Large, prospectively ranbomized clin ical trials have demonstrated its efficacy as a first-line therapy or as an adjuvant to external-beam radiotherapy. It is particularly usefu l when external-beam therapy options have been exhausted, and normal t issue tolerance has been reached. In metastatic prostate cancer, our r ecent survey suggests the formation of a new paradigm: local field ext ernal-beam radiotherapy to the painful index site in combination with prophylactic administration of systemic radionuclides for clinically o ccult metastases.